The capacity of the olfactory epithelium (OE) to recover both anatomically and functionally after injury to near-normal, a capacity that extends throughout life, is unique in the nervous system. However, we know next to nothing about the molecular phenotype of the olfactory stems nor their downstream progenitors, an ignorance that severely hampers our ability to isolate them, understand their regulation, or use them in a controllable manner. We are proposing exploratory and developmental studies designed to address that vast gap in our knowledge. We will isolate three specific types of globose basal cells (GBCs), among whose functionally heterogeneous population, a broadly pluripotent, stem or stem-like cell is found: multipotent GBCs, sustentacular cell- forming GBCs, and transit-amplifying GBCs. The different kinds of GBCs will be defined by the timing of their re-emergence after methyl bromide lesion of the mouse OE and by their expression of one among a group of basic Helix-Loop-Helix (bHLH) transcription factors that will include Hes1 and Mash1. The bHLH TF-expressing cells will be isolated by FACS on the basis of markers on their surface that define them as GBCs and the expression of GFP in parallel with each individual TF (from either a transgen or the endogenous gene locus). For each TF-defined population we will carry out AffyMetrix microarray analysis designed to profile its pattern of gene expression. In addition, mitotically quiescent and BrdU label-retaining GBCs in the normal OE are a potential stem cell population. We will isolate them by FACS as well and subject them to gene profiling. As a consequence of these studies, we will have a comprehensive understanding of resting and activated olfactory stem cells and their downstream progenitors and will be poised to begin hypothesis-driven assessments of functional regulatory pathways. The stem cells of the OE are both easily accessible in adult humans and have a natural propensity to make neurons. Furthermore, the embryonic cells of the olfactory placode, which the adult stem cells resemble in both molecular and functional terms, give rise to the specialized glia of the olfactory nerve, which may promote functional recovery after spinal cord injury. The information gathered here may allow us eventually to use these adult stem cells in treating nervous system damage and degenerative disease. [unreadable] [unreadable] [unreadable]